Field of the Invention
The present invention relates to an amorphous phthalocyanine compound or a mixture of amorphous phthalocyanine compounds in which a crystal form is regulated and which has excellent solubility, and it relates to methods for preparing them. The amorphous phthalocyanine compound or the mixture of the amorphous phthalocyanine compounds of the present invention are useful as near infrared absorption filters, liquid crystal display elements and record/memory materials such as write-once=type optical recording mediums.
Description of the Prior Art
Techniques for applying phthalocyanine derivatives, particularly alkoxyphthalocyanine derivatives to record layers of record/memory materials, particularly optical recording media such as optical discs are well known from Japanese Patent Laid-open Nos. 197280/1986, 246091/1986, 39286/1987 (USP 4,769,307), 37991/1988 and 39388/1988, and other publications. However, phthalocyanines are usually poor in solubility in organic solvents, particularly hydrocarbon solvents having a low polarity, and therefore it is difficult to form thin films by applying the solutions of the phthalocyanines.
On the other hand, Japanese Patent Laid-open Nos. 221461/1989, 50554/1991 and 50555/1991 disclose that the crystallization of the phthalocyanine is accelerated by a solvent treatment or a heat treatment.
For the purpose of solving such problems, the present inventors have developed alkoxyphthalocyanine derivatives as record materials for optical discs, particularly record materials for CD-R which are described in Japanese Patent Laid-open No. 62878/1991, and they have found that in order to apply the alkoxyphthalocyanine derivatives by a spin coating process which is one of solution coating techniques, the optimum concentration of a coating solution is in the range of from 15 g/l to 90 g/l. However, it have also been found that some of the above-mentioned alkoxyphthalocyanine derivatives have a low solubility, depending upon a crystal form, so that they cannot be dissolved up to the optimum concentration, or even once they can be dissolved, they precipitate in a short period of time, so that the coating solutions having a necessary concentration cannot be prepared.
The present inventors have found that the deterioration of the solubility is caused by the association of the alkoxyphthalocyanine. That is, it can be presumed that the association causes crystallization to proceed, and as a result, the solubility in a solvent deteriorates, or that the association causes precipitation from a dissolving state. In particular, a small amount of the association functions as the nucleus of the larger association, and therefore it is necessary to completely remove the association